The present invention relates to a nonwoven fabric patterned with apertures and, more particularly, to a nonwoven fabric patterned with regularly distributed apertures having individual fibers reoriented and entangled together by treating a layer of fibrous material with a high speed water jet.
It is well known to treat a layer of fibrous material (fibrous web) with a high speed fluid jet so as to reorient and distribute individual fibers to form nonwoven fabrics patterned with regularly distributed apertures as disclosed, for example, in Japanese Patent Publications No. 44-23909, U.S. Pat. No. 2,862,251 and U.S. Pat. No. 3,240,657.
In the nonwoven fabric disclosed in Japanese Patent Publication No. 44-23909, relatively many fiber fluffs remain in each of the apertures defined by nonwoven fiber areas, making a contour of this aperture unclear and these nonwoven fiber areas are rope-like without sufficient smoothness. As a consequence, the nonwoven fabric of this prior art is not agreeable to the touch.
The nonwoven fabric disclosed by U.S. Pat. No. 2,862,251 and U.S. Pat. No. 3,240,657 is disadvantageous in that the apertures are not clearly contoured and said nonwoven fiber areas have protuberances which inconveniently limit the nonwoven fabric to a special application. Furthermore, the fiber entangling degree is different in the edges of the respective apertures and in poor surface smoothness the areas defined between these edges, resulting in lower tensile and rupture strengths which inevitably require, in turn, addition of any suitable binder.
It should be noted that these problems are due to the particular techniques employed to form these nonwoven fabrics. More specifically, the former technique is to treat the fibrous web placed on the mesh support with a high speed water jet so that the individual fibers are forced aside under the action of said water jet on the respective intersections (knuckles) at which the component wire material of said support intersects with one another and thereby the apertures are formed. According to this technique, however, the fibers partially project through the apertures (meshes) of said support and partially entangle on said intersections. These fibers are broken as the nonwoven fabric is peeled off from said support upon completion of the treatment and remain as fluffs which make the apertures unclearly contoured. The latter technique, on the other hand, is to interpose the fibrous web between the first support patterned with apertures and having a curved inner surface and the second support of meshes and then to treat said web with the high speed water jet delivered from the side of said first support so that the apertures are formed by displacement of the fibers on the path of the water jet as this water jet forces these fibers aside. According to this technique, the fibers are gathered together to protrude the edges of the respective apertures and, as a result, the fiber is higher than entangling degree is higher in the edges thereof the areas defined between said edges of the respective apertures. Said problem is due to such a fact.
A principal object of the present invention is to provide improved nonwoven fabric having a smooth surface throughout the width of each nonwoven fiber area defined between the apertures, said apertures clearly contoured a strength requiring no addition of binder, soft and agreeable touch and excellent drape characteristics.